Two new Ni(II) Schiff base complexes: X-ray absolute structure determination, synthesis of a N-15-labelled complex and full assignment of its H-1 NMR and C-13 NMR spectra

The Ni(II) complex of the Schiff base of (S)-N-(2-benzoyl-4-chlorophenyl)-1-benzylpyrrolidine-2-carboxamide and glycine (1) [GKCI] and the hemihydrate of the Ni(II) complex of the Schiff base of (S)-N-(2-benzoylphenyl)-1-benzylpyrrolidine-2-carboxamide and 2-aminoisobutiric acid (2) Me(2)GK] were prepared and their absolute structures determined. The conformations of the complexes and their hydrogen bonding are discussed in detail. In complex 2, the repulsion between the benzyl group and an equatorial methyl group should affect the conformation of the benzyl group, distribution of the pi-electron density in this group and distortion of the internal coordination sphere, while for complex 1, only minor conformational changes were expected. H-1 and C-13 NMR data for the N-15-labelled complex 2 were acquired and fully assigned in order to study the influence of pi-electron density of the benzyl group to the long-range C-13-N-15 and C-13-C-13 spin-spin interactions. (c) 2006 Elsevier Ltd. All rights reserved.